A number of copper based alloys, such as GRCop-84, NARloy-Z, or AMZIRC, have been studied for use in high heat flux structural applications, such as hypersonic vehicles and rocket engines, as the alloys may exhibit relatively high thermal conductivity and relatively high-temperature strength. A drawback of such alloys however has been rate at which these materials may oxidize at high temperature, which may ultimately cause deterioration of the alloys, otherwise known as blanching.
To enable or improve the use of these copper alloys at temperatures of up to about 650° C., protective coatings have been applied to shield the copper alloys from oxidation. Protective chromia scales, is an example of such coatings, and are similar to those formed on M-Cr alloys, wherein M may be either Ni, Co or Fe. The coatings may include Cu and Cr, wherein the Cr is present at about 30 volume percent. These coatings have been applied by plasma spray of a pre-alloyed powder as well as co-deposition of Cu—Cr using low temperature arc vapor deposition. A number coatings applied by the above methods have exhibited relatively coarse Cr particles having sizes in the range of 1 to 10 μm.
Nanostructured Cu—Cr coatings have been produced by ion-beam deposition (IBAD) by simultaneous or alternating evaporation from Cu and Cr sources. While this process may result in improved oxidation resistance and reduced particle size, the IBAD process may be considered to be a line-of-sight process, which may not be well suited for interior applications.